Transformer



Sept. 21 1926. 1,600,963

' F. F. BRAND TRANSFORMER Filed June 5, 1925 2 Sheets-Sheet 1 Inventor: Frederick FTBrand y 7:?

Sept. 21 1926. 1,600,963

' F. F. BRAND TRANSFORMER Filed June 5, 1925 2 Sheets-Sheet 2 Fig.2. 6 Figfi.

Inventor-z Frederick ("T Brand, y M H i s Atto ey Patented Septt 21, 1926.

,UNITED STATES 'PAT ENT OFFICE rnnnnnroir 1*. BRAND, or PITTSFIELD, massaonosnrrs, ASSIGNOB r GENERAL nrnc'rnrc comranr, A CORPORATION or NEW YORK.

rmsronmnn;

Application filed June 3;

My invention relates to transformers and more particularly to that form of transformer in which the magnetic core has a winding leg surrounded \by two concentric 5 cylindrical stacks of coils. The invention is an extension of the general principles disclosed in my United States Patent No. 1,536,761, issued May 5, 1925, and its general object is to provide an improved arrangement for'supporting the windings or'coils and for maintaining them in proper relative positions and under proper compression during operation of the transformer. v

A stack of high volt-age windings 0r coils must have a considerable amount of insula- 'tion on the. conductor and. this insulation or an appreciable part of it is commonly composed of material such as ta ing which is com ressible so that the stack may shrink whi e in service under the constant pressure of its supports. In some transformers having two concentric stacks of coils, both coils are of thisch'aracter but the shrinkage of the two stacks may be unequal. It is desir- 2 able or necessary that the stacks be kept tightly compressed to prevent distortion and displacement of the stacksand their comonent coils by the magnetic forces caused y the currents in the coils, particularly under heavy overload 'or short-clrcuit condi: tions. One of the objects of my inventionfis to support the core of the transformer upon the two coil stacks by an arrangement which will distributethe weight .of the core upon the two stacks in a predetermined ratio and per mit the two stacks to shrink, either equally or unequally, without disturbing the degree of compression to which they are subjected by the core. I

If the magnetic centers of the two concentric cylindrical windings are displaced along the winding leg of the core, there exists a force which tends to increase this :displacement. This displacing force may be very great under abnormally heavy load or short circuit conditions if the displacement of'the magnetic centers of the windings is a substantial one. There is no such displacing force, however, if the magnetic centers of 1 winding leg of the core.

proved winding supports sulation which is not 'slble because of the'small quantity used or 1 includes high voltage 1925. Serial No. 84,694.

the windings coincide in position along the A further object of 15 to provide imarranged to permit 3 shrinkage of the two windings, whether such shrinkage is equal or unequal and at the '65 same time to maintain the windings under compression and their magnetic centers coincident'in position along the winding leg of the core. In attaining this result, it may be necessary to compensate for shrinkage of only one of the windings if the other winding is for low voltage operation and has inappreciably compresthe invention, therefore,

because of its incompressible character. 05

The invention will be better understood from the following description taken in con,- nection with the accompanying drawings in which Fig. l is a view in elevation of a transformer constructed in accordance with the invention, parts. beingbroken away to reveal details. Figs. 2, 3, 4, and 5 are similar views in elevation of transformers con structed in accordance with different modifications of the invention, and Figs. 6 and 7 are elevation-and of the transformer shown in Fig. 4.

Like reference characters indicate similar parts in the different figures of the drawings.

The particular transformer. shown in Fig. a core having a winding leg 10 surrounded by two concentric cylindrical 'stacks of windings or coils 11 and 12. The

outer stack of coils 12 is for operation at and a considerable, proportion of the volume of the stack must therefore be insulation so that the stack may shrink and decrease in length appreciably after the transformer is placed in service and subjected to constant heavy compression between I its end supports. The inner stack of coils 11, however, isfor low voltage operation and only a small quantity of insulation is therefore necessary, the incompressible meta1 conductor composing most of the volume of this stack. After being assembled and placed in service, this low voltage stack of plan views, respectively, t

coils 11 will bly but its length will remain substantiall constant throughout its life. The big voltage stack of coils 12 is mounted on a fixed supporting ring 13 carried. on posts 14 above a base 15. The core'is supported by brackets 16 secured to its upper end, the outer ends of the brackets 16 resting on the high and 18 have their inner ends pivoted'to the 20 movable core and their outer ends pivot- V ally supported by a plurality of adjustable sleeves 19 carried on supporting rods 20 fixed to the base 15. By adjusting the positions of the sleeves 19 onthe rods 20, the pressure on the stack of coils 11 may be adjusted andthe magneticcenters of the two stacks of coils 11 and 12 may coincide in position along the winding leg 10 of the core. Top and bottom guides 21secured tothe core have slidable engagement with the supporting rods 19 to guide the ;core. The lower guides 21 carry sleeves 22 withctapered openings containing sets of balls surrounding the rods 19, the balls permitting .the core to settle down with any shrinkage of the 'coil stack 12 but preventing any upward movement of the core or expansion of the coil stack 12. Inasmuch as the 'high voltage stack of coils 12 contains an 40- appreciable amount of compressible insulation and is held in place under considerable pressure due to the weight of the transformer-core, it may shrink and become shorter after the transformer is placed in service. Assuming that this stack of coils 12' is of [uniform construction throughout its length, the magnetic center of the stack is midwa between its two ends and any shrinkage w' be distributed uniformly through the stack. From this and the fact that the lower end. ofthe stack is immovably supported, it will be seen that any, shrinkage of the stack will result in a settling or displacement of its magnetic center egual to one half that of its upper end an of the core. ,In order. that the'magnetic centers of the twocoilstacks 11 and 12 may be maintained always coincident in position along the winding leg 10 of the core,' it is therefore desirable that 00 the inner incompressible low voltage stack 11 be moved or dis laced a distance equal to one half the disp acement of the core; This result is attained .by the construction which has been described because any shrinkag and shortening of the high voltage winding therefore not shrink appreciaset of levers 18' at?v the lower end of the stack. The levers 17 be made to,

levers 25 resting on is accompanied bya corresponding displacement of the core and the Inner ends of the levers 17 and 18 and by a displacement of the low voltage winding 11 and the centers of the levers 17 and 18 equal to one half that of the core.

The form of the invention shown in Fig.2 is applicable and useful in connection with the support oftwo concentric stacks of coils which are so constructedthat there will be about the same amount of shrinka two stacks of coils or where the ifr'erence in the shrinkage of the two stacks will not be great enough to cause an objectionable displacement of their magnetic centers along the winding leg of the transformer. The necessity for maintaining thecoil stacks under tight and unyielding compression is largely to prevent motion of the stacks under load, especially under conditions of heavy overload or short circuit. The magnetic forces in a winding are generally great- .er in'th'e case of a low voltage winding than in that of a high voltage winding. because the current is greatest in the low voltage winding and ,it is the ampere turns in a winding which determine the magnetic flux causing such forces. A winding having a large amount of insulationis usually a hlgh voltage winding and the current which it carries, evenunder short circuit conditions,

is not very great .so that the resulting mag- .very great. For

netic forces are also not this reason, it is sufiicient in some cases f the windings be kept tightly compressedand it is not always necessary magnetic centers of two concentricw'indings coincident along the winding leg of the core. The two concentric stacks of coils 11 and 12 shown in Fig. 2' are mounted on fixed supports 23 secured to the base 15. These coil stacks 11 and'12'surround the wind: ing leg 10 of the magnetic core provided with brackets 24 secured-to its upper end. The outer ends of the oted to the centers of levers 25, the inner ends ofthe levers 25 resting on the inner coil stack 11 and the outer ends of the the outer coil stack 12. The core is thus supported by the two coil stacks and its weight distributed upon them by the levers 25 to keep them tig pressed while in service. As the stacks shrink, the core settles to compensate for the shrinkage and the levers 25 tilt one way or the other to compensate in the shrinkage of the two stacks, the pressure on each stack due core remaining unchanged. Any in uality in the shrinkage of. the two wi of course beaccompanied by a displacement of their magnetic centers along the windin leg 10 of the core. This displacement o the magnetic center of the two stacks will be only one half as great as the difference in e in the brackets 24 are piv-.

tly comfor any inequality to maintain the to the weight of the shrinkage and will be within allowable liniits for the reasons which have been explained.

I the In the form of the invention shown in Fig; 3, th supporting means for the coil stacks 11 and 12 will permit the two coil stacks to shrink unequally while maintaining them under tight compression and at the same time will maintain their magnetic centers in substantial coincidence along the winding leg 10 of the core. The core is supported by brackets 24 and levers 25 which distribute the weight of the core on the two coil stacks 11 and 12 as in the transformershown in Fig. 2. The outer coil stack 12 is supported on fixed supports 23 mounted on the base 15. The inner coil stack 11 is supported by levers 26 which are pivoted at their inner ends to the fixed supports23. The outer end of each lever is pivoted to the outer end of a secondary lever 27. Two rods 28 and 29 are connected by pivot joints from the inner end and center of each lever 27 to the inner and outer ends respectively of one of the levers 25. This construction keeps both coil stacks under constant compression, the levers 25 tiltin to compensate for any ine uality in shrin age. A. consideration of t e arrangement of the levers 25, 26 and 27 and the rods 28 and 29 will also showthat' if either coil stack shrinks, the inner stack 11 will be moved or displaced automatically through a distance equal to one half the amount of this shrinkage so that relativedisplacement of the magnetic centers of the two stacks along the winding leg 10 of the core will be prevented. If both stacks shrink and their shrinkage is una ual, the automatic displacement of the inner stack will be equal to one half thedifierence between the shrinka of the two stacks and their two magnetic centers will remain coincident in position on the winding le of the core.

The construction shown in ig. 4 is applicable Where shrinkage will occur in one coil stack, the shrinkage of the other stack beingsmall enough to be negligible." Here outercoil stack 12 contains an apprecialtlile amount of compressible insulation so t at inner stack 11 is of such construction that any shrinkage will be negli ible. The outer stack 12 is mounted on xed supporting means 23 carried by the base 15. The core is supported by brackets 24and levers 25 which distribute the weight of the core on-the two stacks of coils. The inner incompressible stack of coils 1-1 is mounted on the centers of levers 30, the inner end of each lever 30 beingpivoted to the fixed supportingmeans 23 and its outer end being'connected by a rod 31 tothe outer-end of one of the levers 25. It'will be seen that when the outer stack 12 shrinks, the inner stack will be displaced through a distance substantially equal to 'one.

see 8 half the shrinkage of the outer stack so that the magnetic centers of the twostacks will.

remain coincident 'in position along thewmdin leglOef the core; Fig. 7=isa plani vie-w oi shown in Fig. 4' and indicates how-the levers- 25' and 30' are provided withside extensions 32 between which the rods 31 are connected.

Similar side extensions are of course profigures of the drawing.

The construction ilar to that shown in Fig. 2 except thatthe bottom supporting stacks consists of compensating levers 33 instead-of fixed supporting means asin Fig. 2. Each lever 33 supports the two coil stacks vided in the construction shown in the other 7 the construction just -described and 10 shown in Fig; 5 is simmeans for the two coil 11 and 12 at its inner and outer ends respecj tively and is pivoted at its center to fixed supporting means 34 secured to the base 15. The outer end of each lever 33 is connected levers 25 at the upper ends of the two stacks of coils. Tilting of the levers 25 and 33 compensate 'for inequality of shrinkage in the two coil stacks 11 and seen that the provision of compensating supporting levers at each end of the coil stacks, as shown in Fig. 5, will permit a greater inequality in the shrinkage of the stacks than will be permitted by such levers at one end only of the stacks as shown in Fig. 2. This is so because the angle through which the levers'may be tilted is of course limited. Fig. 6 is a view in elevation of the construction shown in Fi 5 and shows the side extensions 32 on t e levers 25 and 33 between which the rods 35 are connected.

The invention provides means for mainby Letters Patent of the United States is: the stack will shrink in service but the amount of said shrinkage and in the same directiom 3. A transformer including two concentric I cylindrical stacks of windings. and means responsive to shrinkage of the stacks of by a rod 35 to the inner end of one of the 12 and it will be windings for moving one of said'stacksto prevent relative displacement of the magother of said stacks of windings for mov netic centers of the two stncks. ing said first-"stack to prevent relative di s- 4. A transformer including two concenplacement of the magnetic centers of said tric' gllijidrical stacks of windings, means stacks by shrinkage of said second stack. 5 inclu a lever for supporting one of said In witness whereof, I have hereunto set stacks o windings, and means connected to my hand this 29th day of 311% 1925.

said lever and responsive to shrinkage of the FREDERICK BRAND. 

